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This topic is offered as a spinoff of the two years of steady work by RobertDyck on Large Ship.
The original Large Ship design uses Unitary Rotation. This is a concept that seems promising (to me at least), and I would like to see the design move forward toward manifestation in the Real Universe.
A competing design was offered by kbd512. This design is described in the Practical Large Ship topic. The distinguishing feature of this design is the use of counter rotating habitats on a single axle, like a bar bell with weights.
This topic is inspired by the work of a Spanish professor who served many years as an educator, and in those years he created a number of educational videos. The one I found most applicable to the Large Ship design problem is a demonstration of two counter rotating wheels running on parallel axles in a common frame.
I realized immediately that this design is superior to all others that have been proposed.
This topic is offered for development of this variation of Large Ship, with the expectation it will eventually secure funding.
Update 2022/07/30 ... the term "modular" in the title refers to the design feature that the ship can be extended in length, in chunks of paired habitats, or 500 passengers at a time. The starting configuration is a minimal set of two habitats for 500 passengers, and the next logical size is four habitats for a total of 1000 passengers.
It should be noted that there is absolutely NO requirement to pack the ship with the full complement. An expedition of 200 people to some distant part of the solar system would allow for adequate space for each person, along with supplies for a long journey of unknown duration.
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Post #2 is reserved for Specifications and other details needed to lead to a Real Universe manifestation of the vessel.
This post will be updated as specifications are decided upon.
Most of the major specifications will mirror Large Ship (Unitary Rotation) ..
For example, the size of the habitat ring will be identical ....
On the other hand, the dual habitat feature of the "Practical Large Ship" design leads to a requirement for two identical habitat rings.
Atmosphere and other details are intended to follow the carefully worked out design of Large Ship (Unitary Rotation).
Mass is (arbitrarily) set at a maximum of 5000 metric tons, as the ship prepares to leave Low Earth Orbit, as a payload for one of GW Johnson's Space Tugs.
Dr. Johnson is thinking about defining specifications for his Space Tug concept for the Lunar circuit. This would involve giving the Large Ship (or any paying customer) a push toward the Moon, and catching the vessel on it's way back to Low Earth Orbit, so the dangerous and costly expedient of deceleration in Earth's atmosphere is avoided.
It seems clear that with increasing congestion in LEO, any vehicle that risks deceleration in the atmosphere will run a gauntlet of countless unguided objects. Such a vessel would have absolutely NO opportunity or capability to adjust orbit to avoid a collision, so propulsive deceleration will (most likely) become the accepted standard procedure.
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To be clear, this was an option I considered when designing the Large Ship. Two counter-rotating rings cancel gyroscopic effects making the ship easier to steer. But there are problems. This is a trade-off, solving one problem in exchange for creating new problems. With two rings, you just split the ship into two. The space available to passengers and crew is now half size. If anyone wants to visit or otherwise make use of the other ring, they have to travel to the axis of rotation and travel through a narrow tunnel... in zero gravity. And that tunnel requires a rotation bearing, which must include a pressure seal to ensure air doesn't leak out into space. The bearing is constantly rotating, and must bear stress of the momentum of the ring whenever the ship turns. The bearing is subject to constant wear because it's constantly rotating, the two rings are constantly rotating in opposite directions. Well into a 6 month journey, even through the ship is very large, it will feel quite small. The connecting tunnel at the axis of rotation will be so inconvenient, that the vast majority of the time passengers just won't use it. That means they're restricted to half the ship. So the ship has effectively become half size. Furthermore, there will be practically no interaction between passengers in different rings. So there will be two cliques, one from each ring. Working smoothly together as a team, or getting to know each other in preparation to work together on Mars, just won't happen.
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For RobertDyck re #3
Thank you for contributing to this new topic, and for defining the challenges of the counter rotating design.
Part of my motivation for starting this new topic is to try to encourage you and kbd512 to resume work on your respective visions.
I am personally enthusiastic about and supportive of the Unitary Rotation concept, and would like to see you carry it forward.
We hit a snag when we attempted to begin defining details of construction, and then health became a concern for one of our members.
One thing we do NOT need is more speculative writing about some hypothetical imaginary vessel that lives only in the archive of this forum.
If there is a challenge that must be faced in order to move forward, let's try to face it together.
***
Regarding communication between habitats .... there is absolutely no reason whatsoever that anyone should feel in any way isolated from anyone else, with modern digital communications technology.
The "Metaverse" concept of Mark Zuckerberg invention is coming along rapidly as well, but even with just ordinary (2022 era) Zoom and telephone communication, folks in the two habitats can remain as close as teenagers on Earth, to the extent they ** want ** that.
Not ** everyone ** wants to be in a huge crowd ... in fact, in observing the population of Earth, I see a desire on the part of billions of people to get as far away from others as possible. In Space, in a habitat of 250 people squeezed together like sardines, the Internet/Intranet will provide an opportunity to simulate isolation for at least part of the time. Your observation about the challenges of managing social dynamics in space or on Mars (or on Earth for that matter) deserve attention. However, it seems to me that the US Navy experience of sending 250 people to sea for months at a time without creating any kind of social conflict between groups indicates the problem can be solved, through strong management and excellent planning.
Regarding the bearings and other issues, your design is free of those concerns, so please resume work on your very promising vision.
Please chart a course that leads to realistic drawings that can be reviewed by experienced and knowledgeable persons. We do NOT need to fantacize about gobs of money. The Earth of 2022 has millions of highly trained, experienced folks who are out of daily work but still in full possession of professional skills. Your opportunity is to give a lucky few of those folks an opportunity to help with design.
It would also help if you began self-education on how to lead a group of professional volunteers. Your working mode for many years has been the isolated genius, working in his tower and communicating by telegraph now and then.
As a leader, your role is to seek out highly trained, very intelligent people who you can persuade you to help with the millions of details that must be addressed to bring Large Ship (Unitary Rotation) into being.
A key capability is to set up a shared work space for key elements of design.
NewMars has use of a Dropbox folder, and we till have plenty of space for work products.
Both Fusion 360 and Blender are free software that members of a team can use to create models that together will show design elements, and you have shown ability to run both.
kbd512 has given you a suggestion for construction of the pressure hull for Large Ship (Unitary Rotation). That suggestion looks plausible to me, so my suggestion is just put it into the tool kit for the vessel, and go on to other elements that need definition.
kbd512 has challenges to solve that differ from the ones you will be facing, and he hope he will soon resume work on "Practical Ship".
This topic has the distinct advantage of building on the strong points of both your designs, but avoiding the drawbacks.
(th)
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For all .... the design of Large Ship Parallel Axle can be foreseen in the YouTube video in the quote below:
Double gyroscope toc1955 [please note this channel has numerous videos]
https://www.youtube.com/watch?v=bzbVwiI … ev&index=1
I ended up with an assignment, which I'll post here as a reminder:
Adolf Cortel … ask about upscale to space craft....
Update on 2022/07/11 after investigating Adolf Cortel with the assistance of Google ...
YouTube channel toc1955
Adolf Cortel received a PhD in
chemistry from Universitat Autonoma of
Barcelona and has taught high school
physics and chemistry since 1981. His
interests range from development of new
demonstrations, experiments and
workshops to exhibits for science
museums. In Physics on Stage 3 (2003),
he was honoured with a European
Science Teaching Award for his
presentation ‘Simple experiments on the
physics of vision’.Adolf Cortel. Easy observation of infrared spectral lines. Physics Education 2012, 47 (3) , 293-296. https://doi.org/10.1088/0031-9120/47/3/293
Double gyroscope
Watch
Uploaded by: toc1955, May 24, 2009
49.4K Views·149 Likes
( Adolf Cortel 2009) Double gyroscope. [ if interested in easily building a double gyroscope from an available toy, have a look of muy new video , January 2...A PhD in 1981 implies an age on the order of 30 in 1981 (between 25 and 30), so in 2022, on the order of 40 years will have passed.
The gyroscope demo was uploaded in 2009 ...
In thinking about the problem of dealing with the forces at work between the two rotating masses, it occurred to me that in addition to the central shaft bearings, it might make sense to employ magnetic force (attractive or repulsive or both) to transfer force to the frame surrounding the rotating masses.
The elements of a reliable, robust dual habitat space vessel design are evident in the two counter rotating plates shown in the demo. Those plates are mounted in a robust frame, and thus able to withstand the powerful forces that will be at work when the captain needs to change orientation of the vessel.
There is NO need to depend upon the bearings at the centers of the plates. Instead, while the bearings are needed for centering the plates, the actual forces at work will be transferred to the frame using magnetic force.
The magnetic forces needed to keep the rotating habitats centered should ** also ** be design to deflect charged particles that will be arriving from all directions.
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Double Gyroscope at channel toc1955
Below is the url provided by YouTube at the Copy URL button.
https://youtu.be/bzbVwiIeM0M?list=PL1-w … zYzuAOntev
If anyone can figure out how to capture still images from this video, I'd appreciate the help.
In the mean time, I'll add some text to try to capture some of the images I have in mind for the vessel ...
The magnetic fields to keep the habitat firmly in place inside the frame of the vessel will provide another benefit, beside radiation protection.
They will provide "speed of light" response to changes of mass location inside the rotating habitats.
In past posts in this forum, there are warnings about the challenge facing the designer of any rotating space habitat, to preserve integrity of the angular momentum of the rotating structure. Any mass moving on one side of the centerline must be instantly and exactly matched by the same mass moving in the opposite direction on the opposite side of the centerline.
A magnetic force structure around the entire rotating habitat will be able to compensate for momentary imbalances that will be occurring simultaneously and constantly as passengers and crew go about their daily lives.
(th)
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Kbd512 ship also started out doing the double disk but when it can to propulsion that was the heal that stopped its design.
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SpaceNut,
We stopped at my lack of interest in entertaining the fantasies that some people have about Mars colonization ever being practical using chemical propulsion alone. Solid core nuclear thermal does very little to change the practicality of the endeavor, meaning it's "just" slightly less impractical. Since other people aren't interested in exploring more practical alternatives, we're not moving on to economically feasible solutions that have some chance of working. As a result, there's no point to further development of the concept. It's exactly like all the effort expended on development of the fantasy world of Star Trek or Star Wars, because it's a form of escapism that doesn't change technological reality for humanity.
This isn't a form of escapism for me. I'm actually interested in the development of a practical large ship concept that doesn't require entirely new technological development for sake of making the design concept practical. The problem is that nobody else is. I don't care how we "get there", because this isn't an ideologically-based fantasy for me. I don't care who gets credit, nor who does what, so long as the end result is an affordable proposition for the average middle class family. Humanity needs the ability to live on other planets so that we have more room to explore different developmental pathways that at least have the possibility of leading to better outcomes for humanity writ large.
If you want a practical large ship concept, then it won't use chemical propulsion. It won't use scarce or inordinately expensive materials. It won't use technology that's beyond what humanity has already created.
Does anyone else here recall when Elon Musk told Tim Dodd that we need to innovate at a much faster rate, in order to colonize Mars?
My ship concept is an example of taking Elon Musk's very true and very obvious words to heart and then attempting to devise a more practical transport vessel that is not as limited as the upper stage of an orbital class rocket. Since I can't interest anyone else in a practical ship design, we can talk all day long about giant nuclear rocket engines or warp drives or whatever other potentially great ideas that we have, but I think we all know that whatever we come up with is unlikely to transport anyone to Mars within our lifetimes.
I evolved my thinking about what would work acceptably well over time, which demonstrates a willingness to let go of impractical ideas, however appealing they were to me, and then move on to other concepts that would work better or simply work at all.
I think I originally wanted to use fabrics and composites to reduce weight, but then I read enough to know that I can't even find literature on the testing required to accurately determine the strength and longevity of said fibers, so I dropped the idea. However technically intriguing or potentially "great" the use of fabrics could be, there are no good models developed for what we intend to do. I then thought about using Aluminum, but that's not a good material selection for highly stressed parts with little to no inspection or regular maintenance. I settled on the use of a high-strength steel because that material is so easy to work with and low-cost.
RobertDyck wanted to use stainless, but that's a very low-strength steel which results in a high inert mass fraction. I found his fixed all-rotating geometry very appealing, but that amount of mass rotating in one direction produces massive torque from precession that has to be counteracted using gyros which consume a great deal of power, because his ship geometry cannot be treated as a "football", because it's not, so I dropped that idea and moved on to counter-rotation. He kept chiding me for wanting to change "his design" into something he didn't want, so I started a separate topic to please other people. Mind you, I didn't see how "my design", which does not belong to me, it's still RobertDyck's basic idea, mind you, and it's just an idea, and I could care less if we put RobertDyck's name or GW's name or anyone else's name on it, so long as it actually gets built. Basically, that entire exercise only served to demonstrate how we were, collectively, exactly like NASA, and not truly interested in getting things done.
The same was true of the windows. I would also like windows, but I can't have them without sacrificing hull integrity and a significant mass penalty. There was also that minor issue with disorienting most people, causing them to barf. I don't think anyone benefits from painting the walls with vomit, so that idea had to be sacrificed. Practical engineering is frequently in conflict with peoples' wants and desires, but impractical ideas have to be abandoned so that the design can move forward. Otherwise, the design will remain artwork forever, which is pretty to look at and fun to imagine, but doesn't help advance technological reality.
Whenever I see that an idea doesn't work the way I want it to, without significant performance concessions in some other area that matters to the overall practicality of the design, I move on. I won't continue down a dead-end path after it's obvious that my aesthetically-preferred design won't produce the end result I'm after.
What is the end result I'm after?
I want to transport a million people to Mars in a reasonable time frame, say 25 to 40 years, to do it reliably and affordably with a modicum of comfort, and minimize the most severe hazards posed to those passengers along the way. All other design choices are incidental and subordinate to that overriding goal. I thought other people understood that as well. If I have to sacrifice some / most / all of my ideas or someone else's ideas to make that happen, so be it. We want to see a colony on Mars in our lifetimes, so design choices can't be dictated by aesthetics or personal desires. If any design choice detracts from that end goal, then it's history, and good riddance. We only have to come up with something that works well enough to get the job done, and maybe we're all wrong, but time will tell.
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For SpaceNut re development of this topic ....
It should be possible to design a 3D printable 1:1000 scale model of the Large Ship with Parallel Axle counter rotating habitats.
We have already seen that the original Large Ship (Unitary Rotation) can be depicted in Blender. We have two separately created models to show what that particular concept might look like.
The design of kbd512 remains undefined. Hopefully drawings or renderings will show up at some point.
Meanwhile, the work of Professor Cortel provides a solid foundation from which ** this ** topic can proceed.
Referring back to Post #1 of the topic: http://newmars.com/forums/viewtopic.php?id=9124
Updated math with more precision. Mars acceleration for the ship, so 38.0% that of Earth gravity. Radius 37.76 metres from centre of rotation to surface of the floor, 3 RPM. One deck. Circumference 237.25 metres. Ring width 19 metres. This allows 2 isles for cabins, corridors 1.5 metres wide, outside cabins have a window, inside cabins do not. Standard cabin size 4x2.4 metres.
The question I am posing right now is whether a 1:1000 scale makes sense ....
The diameter of a habitat ring would be 75 meters (and change), so the model would be 75 millimeters or 7.5 centimeters.
The width of 19 meters would convert to 19 millimeters or just under 2 centimeters.
These are sizes that are manageable for a small personal 3D Printer.
As I ponder the Westcott Stainless Steel ruler that is available, the size that comes to mind is a yoyo...
Per Google:
But they all end with the same basic conclusion, a yo-yo that weighs about one and three-quarters ounces (49 g) and is about two and five-eighths inches (6.67 cm) in diameter.
How yo-yo is made - making, history, used, parts, dimensions, steps ...
www.madehow.com › Volume 3
How about that! A standard yoyo appears to be 67 millimeters in diameter ....
A ship model on that scale is absolutely doable on a home 3D Printer.
The frame for the vessel would be the 12 edges of a rectangular solid, with the wheels arranged as shown in Dr. Cortel's video.
The frame would provide a sturdy mounting location for all the non-rotating components of the ship.
I think this concept makes sense, both in terms of scale, and in terms of actualization in the Real Universe.
In fact, it is possible that some of the model components from the Blender or Fusion 360 renderings of the Large Ship (Unitary Rotation) might be able to swing over to this design without change, if they were modeled at 1:1000 scale.
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I should give an update as well. One local member wants to continue work on the Large Ship. He wanted to work with me on a novel, and the Large Ship would be in it. But I'm more interested in developing the ship for real. As kbd512 said, a large ship needs advanced propulsion technology. I looked at propulsion, and chemical just is not practical. Gary Johnson gave an excellent treatise on propulsion. I suggested gas core nuclear thermal, specifically open cycle, because it has high thrust and high specific impulse at the same time. Gary likes to cite the theoretical work done in the 1960s, but I cite a paper I found in the early 1990s on NASA's website for NASA Institute for Advanced Concepts (NIAC). NASA had done a study on solid core nuclear thermal in 1990, updating NERVA. In 1974 NERVA could produce 825 second Isp, but theoretical work with computer simulations produced 925 seconds in 1990. About the same time they updated open cycle gas core nuclear thermal rocket, which they believed could achieve 9,000 seconds. That requires high temperature and pressure in the "combustion" chamber. I put quotes on that because a nuclear thermal rocket has a reactor chamber instead of chemical combustion.
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I should report, that for the last few months I've tried to find a girlfriend. The lady I spent time last year broke up with me in March 2021. Her reason is I didn't take time off work to fix her computer. She had changed the password on her laptop, I had taken 2 days off work to try to fix it, but her laptop was locked down with new technology, my tools had difficulty. I had work collecting the census, but taking another day off work on a Monday is not something I was willing to do. Months later she phoned to chat with increasing frequency. She wanted to get back together, but no sex, just meeting for coffee or lunch. Later she didn't want to meet in person, just a voice on the phone and text through Facebook. That's when I decided to create profiles on a few dating websites. It's been an adventure, there are a lot of scams out there. One website I paid for a premium membership, but never got a reply to any message I sent. It became evident that profiles were copied from other dating websites, there's no one here, the whole site is a scam. One lady flirted, until I asked for a video chat. She said her computer couldn't do it, she wanted me to give her money for a new video card so she could do video chat. I told her to just use her smartphone, but she said no. So she sent a scanned image of her driver's license. I didn't ask for ID, she just volunteered it instead of video chat. At first glance it looked Ok, but why was the background around her picture blurry? There's supposed to be a government graphic around your profile picture, so prove it hasn't been altered. So I looked up a North Caroline driver license is supposed to look like. Yes, there were 3 copies of her picture, right size and in the right places, the smallest black-and-white, but again the background is not supposed to be blurry. Birth date in two places, but the second one was the wrong font and wrong text colour. Then I noticed her signature under her picture was a completely different name than the text name on her license. Was this produced by a millennial who never learned to read "cursive"? Then I notice her driver license number was exactly the same as Jane Doe in the sample. Uh huh! Fake! And I told the woman she was a fake, go away. Then I noticed one of the pictures she sent earlier had a logo in the lower-left corner. You couldn't see it when viewing the picture on a smartphone, but could on a PC. When I zoomed in, it was OnlyFans and included the account name. When I looked at that website, I found all the pictures that were sent to me. The profile said she doesn't do nudes any more, but all her old nude pictures are archived for anyone who wants to look. So the person I was chatting with wasn't her, just someone who stole pictures from this website.
Another woman said she wanted to just "hook up". Her profile claimed to be 30, but her pictures looked 22. In chat she claimed she's a brand influencer. Ok, then I should be able to do a Google Image search for her profile picture. I did, and found her. Her dating profile had an initial, but the celebrity profile I found had her full last name, and links to her Facebook, YouTube, Instagram, and TicTok. The celebrity profile had her full birth date, so she's 22. I said she looked 22; nailed it! She said she has enough money to travel, and wanted to meet somewhere for a vacation, asked where I would like to go. Ok, so I suggested she come here. She pays for her own airfare, I'll pay for everything once she's here. But then she asked me to send money for her airfare. Oh... so it starts. So I asked for a video chat, to ensure I was actually talking to her. She got upset, claiming I would want her ID next. I said no, and mentioned I found her online. She got upset that I found her Instagram. Why? So I looked more closely. I found all the pictures she sent to me; all except the topless one. Then I noticed a link at the top of her Instagram to another website. When I followed that, it was ManyVids, with nude videos. Many of the videos had a logo for PornHUB. And a link for OnlyFans. Oh... I'm not sure I want to be with someone who does porn. I sent a message to her Instagram to see if it's really her. She responded on the text app we were using. So it may have actually been her, but something was wrong. Anyway, she asked me to stop texting her.
Through the dating website for serious relationships, I received hundreds of responses, but mostly from women in USA. Some from all over the world, but none from my city or province. One lady claimed to be from Toronto, but her description of herself didn't quite match her picture. Then she claimed to have travelled to Paris France, a mugger took her debit card and forced her to give up PIN number. She didn't have any money to get home. Uh huh! And I have a bridge to sell in Brooklyn. That's one of the classic scams.
Many ladies refuse to fill in their location. When I asked one lady to fill in her location, she asked where I am. She claimed to live in the same city. Uh huh, suspicious. Then said she just wants to be friends with benefits. But before I could respond, she said is married with 2 children, but her husband is out of the city for 4 months for work. In her words, she wants someone to f*** when she wants to f***. Yes, she used the asterisks. I'm not going to do that, and said so. So she created another profile, same first name but a number instead of her last name, and same profile picture. So I asked if she's still looking to cheat on her husband. No response. Then a third profile, same first name and different picture, but obviously the same woman. So I asked to meet, thinking I would take her phone and call her husband. But no response. Then a 4th profile, different name and picture, but obviously from the picture the same woman. this time she claimed to be in California, but her phone number starts with an area code for a different state. Then another profile, same first name as the first profile, different picture but wearing the same outfit as the first profile.
But I did seem to get along with 2 ladies. Both wanted to get serious, and move up to Canada to live with me. One from Texas, claimed her father was from Texas but her mother lives in Ghana. She has brothers who live with her mother in Ghana, but she lived with her father until adulthood. If that's the case, she should be black, so why did her profile picture look hispanic? If her father was hispanic, then she should still be half black. Saw several YouTube videos about romance scams. One recommendation was to do a Google Image search on her profile. Got a hit; she's a porn star. Lots of porn videos, and all profile pictures are from porn sites. One wearing a nice dress, but the porn site has the exact same picture, but then more pictures with her top pulled down to reveal her tits, skirt hiked up to reveal her pussy. When I challenged her about this, she at first tried to deny it. So I sent links to two porn sites where her profile pictures came from. One website described the porn actress real name, birth date, name of her husband and year married, and name she performs under. So the woman I was texting with admitted that isn't her. She sent pictures of what she really looks like. A great big fat black woman. Uh huh! At least she doesn't do porn, but that's a hard no.
So that leaves a 36-year-old woman from Missouri. An immigrant from Finland, and wanted money to pay her lawyer for a court hearing to resolve an issue over her green card. Oh... money. But we had chatted with text for 2 months. I said no, but she whined and, well, wore me down. I shouldn't have, but sent $1500 in US funds. She claimed the court hearing was successful, she got her green card, but it'll take 8 weeks to arrive. Then she claimed her lawyer wants money for past work, when they tried to deport her. Wait, if she was sponsored by her uncle as a family member, then why would they deport her? She claimed she filed as a refugee. But again, if her uncle sponsored her, then she's not a refugee. What? So now her lawyer wants $3800 more, and is holding her passport from Finland until he gets it. She needs ID to enter Canada. I looked up the rules, she could enter with a birth certificate. When I told her this, she said her lawyer is holding that too. She didn't mention that earlier. So I said I can't send any more money until she gets here. She could enter Canada using her green card, but will have to wait until that arrives. She doesn't want to wait. I offered to have a friend drive her car up to Canada, then I could hold her car as collateral. She didn't say no exactly, because it would mean her car would be here for her own use once she gets here. I didn't ask to transfer ownership, just ensure she gets here. But she said she would talk to her uncle. She didn't want to bring him into this. But if she was sponsored by him, he should have been brought in right away. Another complication is she says the lawyer wants her. She's the one who initiated contact with me via the dating website. She claims she showed a picture of me to the lawyer. He called her an ingrate. But he didn't do his work pro-bono. We'll see what happens.
::Edit:: Well, the 36-year-old got upset when I wouldn't send any more money. And got upset when I insisted on a video phone call, where I can see here and talk to her at the same time. She broke up with me. So it's just a scam. That's 3 months of my life I won't get back.
Last edited by RobertDyck (2022-08-02 05:53:07)
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For RobertDyck re #11
While this topic was set up to encourage and to report on development of a specific version of Large Ship, your post is a powerful reminder that in the end, all this work is done to move humans from Earth to Mars (or other Solar System destinations) and the psychological needs of the passengers and crew MUST be considered in planning the vessel.
As a preliminary move in this direction, I have retained the physical dimensions of a habitat ring from Large Ship Unitary Rotation (LSUR) while adopting the 250 passengers per ring proposal of kbd512 for his Practical Large Ship. In this single step I have increased available volume per resident by a factor of 4.
In addition, I have chosen to retain the rotation rate of 3 RPM, and the atmosphere prescription of 3-5-8 to insure the ability to transition to EVA equipment without prebreathing.
In addition, I have chosen to adopt the proposal of GW Johnson, to offer Space Tug services to launch the vessel toward Mars, and to receive the vessel for deceleration upon approach to Earth.
Finally, I have chosen to adopt the mass specification suggested by GW Johnson of 5000 tons as seen by the SpaceTug at Earth departure.
With these specifications, I am hoping it is possible to proceed from words to models in mathematical form, and from those to images and physical models at 1;1000 scale.
I see nothing that would stand in the way, which is fortunate, because whatever show stoppers there may be are hidden.
(th)
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For GW Johnson,
Post #12 proposes a mass of 5,000 tons for a Large Ship at Earth departure.
The vessel is to be given a shove from Earth by one of your Space Tugs, and it is to be decelerated upon return from Mars by another. The mass of the vessel upon return from Mars will be less by the amounts of:
1) Propellant needed to leave Space Tug and enter Hohmann transfer orbit.
2) Propellant needed to accelerate to enter Mars Low Orbit
3) Propellant needed to accelerate to leave Mars Low Orbit
4) Propellant needed to fine tune the flight back to Earth
5) Propellant needed to dock with Space Tug on return to Earth
Whatever mass is left over is available for the design team to allocate to physical structures, supplies, passengers and crew.
By any chance, have you already covered this scenario in one of your flight plants?
(th)
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Tom:
If I understand correctly, this is the chemical 2-way "big ship" assisted by a space tug only at Earth, and yes, I covered that in my "big ship" study and submitted paper.
There is the habitat and cargo section, at 5000 tons, which has no propulsion by itself, which I usually referred to as "dead head payload". To this you add the "big ship" propulsion stage, and for tug assist, there is a second propulsion stage that we call the "space tug" that never escapes from Earth. The space tug operates between LEO and an elongated elliptical orbit about the Earth.
The confusion might be what is referred to as the "big ship". One could just as easily use that term for the 5000 ton habitat plus its enormous propulsion stage, which is what I did in the paper. Fig 2 of the paper has this concept of dead head payload pushed by a propulsion stage. I mostly used the term "dead head payload" for the unpropelled portion of the "big ship" item. The 5000 tons was arbitrary, everything is proportional to that dead-head payload mass. If it is 500 tons, divide my numbers by 10. If it is 10,000 tons, multiply my numbers by 2. Etc.
Fig 7 in the paper shows the flights to and from Mars, assuming Hohmann min energy transfer, for this 2-way ship assisted by only an Earth tug scenario. The "big ship" in this context is the dead-head payload plus its propulsion stage, to which a space tug propulsion stage is attached in LEO. The tug takes this cluster to the elliptical perigee speed, and detaches. The "big ship" propulsion stage then burns to finish escaping onto the interplanetary trajectory, then burns again for course correction, then burns yet again to arrive unassisted into LMO.
It is not refilled at Mars in this scenario. What I assumed was the dead head payload mass is still 5000 tons after unload and reload in LMO. The "big ship" propulsion stage then burns to get onto the trajectory home, then again for course correction, and one last time to enter not LEO, but that odd elongated elliptical orbit about Earth. That's it for the "big ship" propulsion stage. It is out of propellant.
Meanwhile, the space tug, left in that elliptic orbit after detaching from the big ship, burns unladen to re-enter LEO, where it is refilled on orbit. Then when the "big ship" is returning into that elliptic orbit from Mars, the space tug burns unladen to enter the elliptic orbit just as the "big ship" is also at that perigee. It docks with the big ship, and then burns laden (with the depleted "big ship" as its payload) to return to LEO, where both can be refilled on orbit.
The propellant quantities and corresponding inert mass sizings for this scenario are in Figure 8 of the paper. The corresponding launch propellant estimates to send these propellant masses to LEO are given in Figure 9 of the paper for the 2-way Earth tug only scenario. There is a note at the bottom of figure 9 that the "landing boat" propellants needed at Mars to unload and reload the 5000 ton dead head item are not included in the estimates! Otherwise, all the propellants for the entire mission are sent up from Earth in this scenario.
What we have at launch for Mars is the 5000 ton dead head item, plus a propulsion stage of 710 tons inert plus 22,988 tons of propellant. The space tug that pushes it off has 1243 tons of inert and is fully loaded with 40,187 tons of propellant.
What we have upon entry of the big ship into the elliptic orbit upon its return to Earth is the same 5000 tons dead head, with a propulsion stage that is 710 tons inert and zero propellant left. That is the payload for the space tug to recover back into LEO, and it is quite a bit lighter than what was pushed off at launch to Mars (by 22,988 tons). So, the space tug is the same 1243 tons of inert, but you only need to put 10,071 tons of propellant aboard it for this recovery phase of the mission.
I hope that helps. I hope I guessed your intent correctly.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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For GW Johnson re #14
Thank you for your detailed reply, and for confirmation you have already covered the Earth-push and Earth-catch scenario.
The difference I am proposing is a variation that your previous work may cover ...
The ship of ** this ** topic differs in several respects from the Large Ship of RobertDyck, and the Practical Ship of kbd512.
You have contacted the Zoom hosts about a meeting this evening.
If all goes well, I may be lucky enough to catch you for a review of the scenarios for ** this ** version of Large Ship.
(th)
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